1. Technical Field
This invention relates to an antenna connecting structure and an antenna connecting method for an antenna device mounted in a vehicle such as an automobile, and more particularly to the connection between a shielded cable (connected to a circuit such as a feeder circuit and a transmit-receive circuit) and an antenna conductor of the antenna device.
2. Background Art
Conventionally, a vehicle such for example as an automobile is equipped with an antenna device (serving as a radio antenna (AM•FM), a television antenna or the like) having an antenna conductor of a predetermined shape affixed to the vehicle. For example, in the case where such an antenna device is used as a radio antenna, a coaxial cable is usually used to connect the antenna conductor to a circuit such as a feeder circuit and a transmit-receive circuit mounted on a vehicle body.
The coaxial cable is a kind of shielded cable, and is of a multi-layer construction including a core wire (conductor), an inner sheath covering an outer peripheral surface of the core wire and extending in a longitudinal direction of the core wire, a shielding member covering an outer peripheral surface of the inner sheath and extending in the longitudinal direction, and an outer sheath covering an outer peripheral surface of the shielding member and extending in the longitudinal direction.
Therefore, when this coaxial cable is to be connected to the antenna conductor, first, part of the outer sheath is cut off or removed so as to expose one end portion of the shielding member, and then part of the shielding member is removed so as to expose one end portion of the inner sheath, and then part of the inner sheath is removed so as to expose one end portion of the core wire. In this exposed condition, the coaxial cable and the above circuit are connected together at their relevant portions usually by soldering (see, for example, Patent Literature 1).
More specifically, in an antenna connecting structure 100 disclosed in Patent Literature 1, a coaxial cable 101 is used as a feeder for connecting an antenna conductor (antenna radiation conductor) of an on-board high-frequency equipment to a feeder circuit as shown in FIG. 4, and this feeder circuit is provided on a circuit board 102. This coaxial cable 101 includes a core wire (inner conductor) 103 provided at a center portion thereof, and an inner sheath (inner insulating layer) 104 covering an outer peripheral surface of the core wire 103. The coaxial cable 101 further includes a shielding member (outer conductor) 105 in the form of a braid covering an outer peripheral surface of the inner sheath 104, and an outer sheath (outer covering member) 106 covering an outer peripheral surface of the shielding member 105.
A signal wiring-purpose soldering land 107 (to which the core wire 103 of the coaxial cable 101 is adapted to be soldered) and a grounding-purpose soldering land 108 (to which the shielding member 105 is adapted to be soldered) are formed on a surface of the circuit board 102, and are spaced a predetermined distance from each other.
The core wire 103 of the coaxial cable 101 is connected by solder 107a to the signal wiring-purpose soldering land 107, and the shielding member 105 is connected by solder 108a to the grounding-purpose soldering land 108.
The signal wiring-purpose soldering land 107 is connected to the feeder circuit (not shown), and the grounding-purpose soldering land 108 is connected to the ground (not shown).
[Patent Literature 1] JP-A-2006-41360 (FIG. 1)
When connecting the coaxial cable (shielded cable) 101 to the antenna device as shown in Patent Literature 1, the connection of the core wire 103 to the antenna conductor, as well as the connection of the shielding member 105 to the ground, is usually effected by soldering, and therefore there has been encountered a problem that much time is required for this connecting operation.
Furthermore, the amount of solder used in the soldering operation affects an antenna performance (for example, an impedance), and therefore the amount of the solder must be controlled, and this is cumbersome and may lead to a possibility that the efficiency of the operation is lowered.